Atmospheric characterization systems and methods

ABSTRACT

The present disclosure is of an atmospheric characterization system that has a central processing board that has a first and a second communication interface. Further, the atmospheric characterization system further has a first precision temperature sensor that is communicatively coupled to the central processing board via the first communication interface and positioned a distance from a first side of the processing board, wherein the precision temperature measures a first temperature and transfers data indicative of the first temperature to the central processing board. In addition, the atmospheric characterization system has a second precision temperature sensor that is communicatively coupled to the central processing board via the second communication interface and positioned the distance from a second opposing side of the processing board such that the first precision temperature sensor and the second precision temperature sensor are equidistance from the processing board and a distance between the first precision sensor and the second precision sensor is a predetermined distance, r, and the second precision temperature sensor measures a second temperature and transfers data indicative of the second temperature to the central processing board simultaneously with the transferring of the first temperature. Additionally, the atmospheric characterization system has a processor that receives the first temperature and the second temperature and calculates a value indicative of atmospheric turbulence based upon the first temperature and the second temperature, wherein the value indicative of the atmospheric turbulence is used for designing, modifying, calibrating, or correcting an optical system.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority to U.S. Provisional Patent ApplicationSer. No. 62/515,299 entitled Atmospheric Characterization Systems andMethods and filed on Jun. 5, 2017, which is incorporated herein byreference.

BACKGROUND

As engineers and scientists work to refine free-space optical systemsthat operate over long terrestrial ranges, it is helpful to betterunderstand, characterize, and quantify the atmospheric properties of theenvironment. One such atmospheric property of interest is therefractive-index structure coefficient, or Cn², which describes smallchanges in the base atmospheric refractive index. Over very shortdistances, small index of refraction changes usually cause negligibleproblems to all but the most demanding optical systems, such asinterferometric systems, but can have a large effect on Optical PathLength (OPL) as short as 1 km.

At the lowest level of understanding, index of refraction fluctuationsin the atmosphere originate with turbulent air motion. The source ofatmospheric turbulence originates from temperature gradients on thesurface of the earth as solar radiation and daily weather patterns causea heating and cooling cycle. The large-scale temperature gradient fromthe surface of the earth to upper atmosphere that is both easilymeasured and causes atmospheric turbulence also applies to very smalltemperature gradients that are not separated by such vast distances.These small temperature gradients are considered randomly distributedthroughout a larger temperature gradient. The index of refraction of airis sensitive to fluctuations in temperature yielding a randomlydistributed index of refraction for air through a slant or horizontalpath of small temperature gradients, setting the groundwork forunderstanding the differential temperature impact on therefractive-index structure coefficient.

Systems like large terrestrial telescopes, free-space lasercommunication systems and High Energy Laser (HEL) free space systemsrequire a stable index of refraction for optimum operation. It isunderstood that Cn² is the most disruptive close to ground level solarge telescope construction projects take the ground level atmosphericproperties into consideration and are consequently built in locationswith higher altitude or, at a minimum, on the highest floor ofuniversity buildings away from ground atmospheric turbulence. Mobile HELsystems rarely have the luxury of selecting an ideal operatingenvironment and therefore must either be designed to operate with pooroptical atmospheric properties or the environmental impact onperformance must be understood and estimable.

The measurement of the refractive-index structure coefficient, Cn², hasbeen used for several specific purposes related to HEL testing. Recenttest events have utilized Cn² measurement at various locations forcomparison to historic models such as the Hufnagel-Valley 5/7 model, tohelp understand performance of HEL in relation to atmosphericturbulence, and to offer comparison of equipment used to collect Cn².While not specifically related to HEL testing, designers investigatingadaptive optics systems that are being developed for imaging in highturbulence also understand the atmospheric turbulence parameters theyare operating in.

Collection of measured Cn² data compared to historic models such asHufnagel-Valley 5/7 model, High Energy Laser End-to-End OperationalSimulation (HELEEOS), and the Tunic Model is of interest to understandwhich models closely predict Cn² per environment and altitude. As moreprecise models are developed and compared to existing models, thequantifying for accuracy will continue to measure Cn² at a test site.

HEL field tests are heavily instrumented with a vast array of high speedcameras, beam monitoring and evaluation systems, meteorological datacollection systems, and atmospheric scintillation measurement devices.One such atmospheric propagation effects on a HEL system includetransmission losses, turbulence, and thermal blooming. The measurementsfrom all these devices are critical to understanding the performance ofthe HEL under test, with a focus on the measurement of Cn².

Standalone adaptive optics systems suffer from similar environmentalperformance factors as HEL systems except for thermal blooming. Adaptiveoptics systems under test will have a similar set of instrumentation asHEL tests to include devices that measure atmospheric turbulence. Theamount of atmospheric turbulence that is induced by environments is alsoof interest during the adaptive optics design process. With the goal ofthe adaptive optics system to correct the outgoing wavefront andcompensate for atmosphere induced optical aberrations, the amount ofatmospheric turbulence will drive the depth of control required for theadaptive optics system. When using a deformable mirror to correct thewavefront, the amount of peak to valley travel available limits theamount of turbulence that can be corrected. Measurements of therefractive-index structure coefficient, Cn², in real environments canhelp engineers estimate maximum wavefront error and select adaptiveoptics with sufficient range of motion to control the turbulence.

Known measurement methods of atmospheric turbulence data includes

Scintillation Detection and Ranging (SCIDAR)—imaging the shadow patternsin the scintillation of starlight.

Low Layer Scidar (LOLAS)—small aperture version of SCIDAR designed forlow altitude profiling

Slope Detection and Ranging (SLODAR)—operated by detecting thebackscatter from atmospheric conditions.

Multi-Aperture Scintillation Sensor (MASS)—optical sensor that createstwo images of a single target on a focal plane array to estimateatmospheric scintillation.

Moon Scintillometer (MooSci)—uses multiple photoelectric diodes atvarious distances to monitor minor changes in light reflected from theMoon.

Radio Detection and Ranging (RADAR)—RAdio Detection and Ranging mappingof atmospheric turbulence.

Differential Image Motion Monitor (DIMM)—optical sensor that creates twoimages of a single target on a focal plane array and uses statisticalarea of interest tracking to estimate atmospheric scintillation.

Atmospheric Characterization System (ACS—Shack-Hartmann WavefrontSensor)—optical system that measures changes in wavefront from a sourcebeacon.

Scintillometer (Popular name brands are Scintec and Kipp &Zonen)—commercially available scintillation measurement device.

Balloon-Borne Thermometers—temperature sensing devices that estimateatmospheric characteristics.

Many atmospheric turbulence profiling systems sampled are opticalsystems that image a beacon or target from known distance and thencompute an estimate of atmospheric turbulence based on the sensor data.All the listed atmospheric turbulence profiling systems, except theBalloon-Borne Thermometers, measure an integrated path of turbulence andnot turbulence at a nodal location. Additionally, several of theatmospheric profiling systems are path weighted and require furtheranalysis.

Advantages of optical atmospheric profilers for measuring Cn² whentesting with HEL or adaptive optics systems are that the systems areaccepted by the test community as the metric of turbulence measurements.Atmospheric characterization systems measuring the same optical path asa HEL device under test essentially use the same mechanism as an imagingsensor for an adaptive optics system but without any correction foratmospheric effects. Many optical profilers have graduated fromuniversity use and become commercial products, which implies dataintegrity, system stability, and system reliability. These systems canalso profile vast horizontal and vertical distances without the need forusing multiple characterization devices.

Disadvantages to measuring Cn² with an optical system share some oftheir strengths. The downside to measuring an integrated opticalturbulence path is that the path is averaged and weighted. Turbulenceinduced by micro-meteorology over various terrain is essentially pathaveraged and the instruments do not have the ability to specificallydetermine the turbulence-generating at any a single point along theoptical path. Optical atmospheric turbulence characterization devicesare also designed for a minimum and maximum path which they can measure,250 m-6000 m. (BLS900, 2017). Many optical atmospheric turbulencecharacterization devices also require a beacon, or light source, toimage down range. The addition of a down range component implies twodevices, two power sources, and some amount of alignment and setup priorto taking a Cn² measurement. Finally, the majority of Cn² measurementdevices are expensive initial investments, and in some cases, costprohibitive to own and operate.

SUMMARY

The present disclosure is of an atmospheric characterization system thathas a central processing board that has a first and a secondcommunication interface. Further, the atmospheric characterizationsystem further has a first precision temperature sensor that iscommunicatively coupled to the central processing board via the firstcommunication interface and positioned a distance from a first side ofthe processing board, wherein the precision temperature measures a firsttemperature and transfers data indicative of the first temperature tothe central processing board. In addition, the atmosphericcharacterization system has a second precision temperature sensor thatis communicatively coupled to the central processing board via thesecond communication interface and positioned the distance from a secondopposing side of the processing board such that the first precisiontemperature sensor and the second precision temperature sensor areequidistance from the processing board and a distance between the firstprecision sensor and the second precision sensor is a predetermineddistance, r, and the second precision temperature sensor measures asecond temperature and transfers data indicative of the secondtemperature to the central processing board simultaneously with thetransferring of the first temperature. Additionally, the atmosphericcharacterization system has a processor that receives the firsttemperature and the second temperature and calculates a value indicativeof atmospheric turbulence based upon the first temperature and thesecond temperature, wherein the value indicative of the atmosphericturbulence is used for designing, modifying, calibrating, or correctingan optical system.

Further, the present disclosure describes an atmosphericcharacterization method that comprises the steps of: (1) measuring afirst temperature via a precision temperature sensor communicativelycoupled to a central processing board and positioned a distance from afirst side of the processing board; (2) measuring a second temperaturevia a second precision temperature sensor communicatively coupled to thecentral processing board and positioned the distance from a secondopposing side of the processing board such that the first precisiontemperature sensor and the second precision temperature sensor areequidistance from the central processing board, and the distance betweenthe first precision sensor and the second precision temperature sensoris a predetermined distance, r; (3) transferring data indicative of thefirst temperature and the second temperature sensor to the centralprocessing board simultaneously; (4) receiving, by a processor, thefirst temperature and the second temperature; (5) calculating a valueindicative of atmospheric turbulence based upon the first temperature,the second temperature, and the distance, r, and (6) designing,modifying, calibrating, or correcting an optical system based upon thevalue indicative of the atmospheric turbulence.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure can be better understood with reference to thefollowing drawings. The elements of the drawings are not necessarily toscale relative to each other, emphasis instead being placed upon clearlyillustrating the principles of the disclosure. Furthermore, likereference numerals designate corresponding parts throughout the severalviews. The present disclosure contains at least one drawing executed incolor. Copies of this patent or patent application publication withcolor drawing(s) will be provided by the Office upon request and paymentof the necessary fee

FIG. 1 is a diagram that depicts the exchange of heat flux leading toturbulence, which illustrates how heat flux transitions through thelower atmosphere.

FIG. 2 is a diagram illustrating Snell's Law and the material changeinterface.

FIG. 3 is a diagram illustrating how a ray bends as it transitions frommaterial to material over a distance.

FIG. 4 is a diagram illustrating the right-angle relationship asdescribed with reference to Snell's Law.

FIG. 5 is a graph depicting the change in height per distance per angleof the index of refraction.

FIG. 6 is a graph depicting the maximum phase shift per distance whencompared to a base index refraction and an index of refraction value asthe maximum atmospheric turbulence within it.

FIG. 7 is four graphs representing values used for change of temperaturecalculations extracted from a daily whether report.

FIG. 8 is a graph representing the change in atmospheric turbulence inrelation to the time of day.

FIG. 9 is a graph depicting temperature sensor resolution in relation tothe time of day.

FIG. 10 is a graph depicting a higher resolution sensor used to obtainthe atmospheric resolution in relation to the time of day.

FIG. 11 is a graph such as depicted in FIG. 10 enlarged to better showthe differences in the higher resolution sensor.

FIG. 12 is a block diagram of an exemplary atmospheric characterizationsystem in accordance with an embodiment of the present disclosure.

FIG. 13 is a more detailed block diagram of the atmosphericcharacterization system as shown in FIG. 12.

FIG. 14 is a diagram of exemplary solar radiation shields used in theatmospheric characterization system as shown in FIG. 12.

FIG. 15 is a cross-sectional view of one of the solar radiation shieldshown in FIG. 14.

FIG. 16 is a flowchart depicting the architecture and functionality ofthe atmospheric characterization system shown in FIG. 12.

DETAILED DESCRIPTION

The present disclosure is an atmospheric characterization system thatmeasures atmospheric turbulence over a period of time, which can them beused to design, modify, or calibrate optical systems to result in moreaccuracy of the optical system. The atmospheric characterization systemcomprises a central processing board. Additionally, the atmosphericcharacterization system comprises a first temperature sensorcommunicatively coupled to one side of the processing board a distanced₁ from the processing board. Further, the atmospheric characterizationsystem comprises a second temperature sensor communicatively coupled toan opposing side of the processing board the same distance d₁ from theprocessing board. In operation, the differential temperature of thefirst and second sensor is used to calculate atmospheric turbulence at aparticular time and location. This data may then be used to design,modify, or calibrate an optical system so that the optical system ismore accurate.

Thus, the measurement approach used for present disclosure is adifferential temperature sensor (DTS) system with high resolution, lowcost, digital temperature sensors that can measure the refractive-indexstructure coefficient, Cn², of turbulent air. In one embodiment, acustom integrated set of digital temperature sensors are used for thedata collection with a key aspect of sensor selection that there must bea very small temperature resolution.

The technological improvement of using the constructed DTS system arethat the sensors measure a ‘nodal’ location and not the typicalintegrated path of an optical atmospheric characterization device. Theatmospheric turbulence is only measured where the sensor is located. The‘nodal’ nature of the DTS sensors implies that there is not a minimummeasurement path, system path averaging, or additional hardware to setup and align. Multiple DTS systems can be combined to measure anatmospheric turbulence ‘area’ that is not possible to measure withoptical devices. The concept of the final DTS system is a low cost, lowpower consumption, extremely portable and accurate device.

To better understand the present disclosure, this disclosure begins witha description of the Refractive-Index Structure Coefficient, Cn2, andpresents how it is employed to describe the turbulence in theatmosphere. This includes its dependence on, most importantly, local andsmall temperature gradients. This is followed by the system leveldefinition of the component requirements for the atmosphericcharacterization system of the present disclosure.

For the purposes of the present disclosure, it is assumed that most ofatmospheric turbulence is driven by temperature changes in theenvironment with a local background mean pressure and temperature. Otherexperiments have considered the effects of humidity fluctuations, windspeed, wind direction, and solar loading as additional sources ofatmospheric turbulence. The source of these changes comes from theintensity of the vertical convection transfer of heat, moisture, andmomentum during the day that is determined from the surface heat fluxand thermal structure of the entire mixed turbulent layer.

The exchange of heat flux which leads to turbulence can be seen in FIG.1, which shows how heat flux transitions through the lower atmosphere.On the left (a) of FIG. 1 is a vertical profile of the mean potentialtemperature within and above a forest canopy during the daylight hours.There is a stable layer within the forest canopy that extends to anunstable layer and then transitions to a near-neutral layer. Air abovethe near-neutral layer becomes stable and has minimal turbulence. Thevertical dashed lines show the deep movement of air parcels within theboundary layer.

The right side (b) of FIG. 1 describes the heat flux that is observedunder conditions of panel (a). Heavy vertical arrows indicate thedirections and magnitude of vertical fluxes of heat. From FIG. 1 panel(b) larger magnitudes of heat flux correlate to turbulent and unstableair. Assuming a local-closure approximation for the vertical heat flux adirection and magnitude of the flux is defined by the vertical gradientof the potential temperature. This can be described mathematically whereθ is potential temperature, w is the vertical component of wind, K_(H)is the thermal diffusivity of a substrate, and z is the vertical spacecoordinate (altitude), which is described in the following equation:

$\begin{matrix}{\overset{\_}{\overset{.}{\theta}\overset{.}{w}} = {{- K_{H}}\frac{\partial}{\partial z}\overset{\_}{\theta}}} & {{Equation}\mspace{14mu} 1}\end{matrix}$

Because the physical source of the index of refraction variations isderived from the temperature gradient in turbulent air motion, the indexof refraction can be modeled as the sum of the mean index of refraction,n₀, and the randomly fluctuating term, n₁({right arrow over (r)},t):

n({right arrow over (r)},t)=n ₀ +n ₁({right arrow over (r)},t)  Equation2

where {right arrow over (r)} is a three-dimensional position vector, andt is time. These small fluctuating index of refraction terms areinconsequential for short distances but can alter a beam wavefront,Optical Path Length (OPD), or position at longer distances.

To understand the impact of n₁({right arrow over (r)},t) on an opticalsystem, a simple geometrical optics model is used that utilize Snell'sLaw,

n ₁ sin(θ₁)=n ₂ sin(θ₂)  Equation 3

where n₁ is the first material index of refraction, θ₁ is the angle theray strikes the interface of the two materials, n₂ is the secondmaterial index of refraction, and θ₂ is the angle the ray leaves theinterface of the second material. This is illustrated in FIG. 2.

Expanding Snell's Law from two materials to 5-10 over distances of 100meters starts to create notable differences in ray height from where theray would land without a change in index of refraction. FIG. 3illustrates the basic concept of how a ray will bend as it transitionsfrom material to material over a distance. FIG. 3 depicts ray tracingthrough isotropic volumes of different refractive index compared tohomogeneous volumes of similar refractive index.

Note that calculations to understand the real impact changes in index ofrefraction cause over a 100-meter path at various angles usingrearranged terms in Snell's law and basic geometry may be performed. Ifthe change of index of refraction were constant, then the traced rayswould still arrive at their target. If the change of index of refractionis varying in time, then the arrival angle and arrival height changesfrom moment to moment. This causes blur and distortion of the image orbeam shape.

For analysis a modified Snell's Law, Equation 4 calculates the anglewhen moving from one volume index of refraction to the next. Thethickness of the refractive index volumes was then used to calculate theheight of where the ray would strike the next volume of refractiveindex. Equation 5, which is derived from finding the height of aright-angle triangle, is used to solve the height value.

$\begin{matrix}{{\sin^{- 1}( \frac{n_{1}{\sin ( \theta_{1} )}}{n_{2}} )} = \theta_{2}} & {{Equation}\mspace{14mu} 4} \\{{b( {\tan \; \theta_{2}} )} = a} & {{Equation}\mspace{14mu} 5}\end{matrix}$

Basic calculations are shown in Tables 1A and 1B and then illustrated inFIG. 5. The tables were calculated by following a ray that is startingat distance 0 and then evaluated every 5 meters, b, up to 100 meters.The starting incident angle, θ₁, was set to 60 degrees. The change inheight, a, per 5 meters, b, was calculated by using Equation 4 to yieldθ₂ and then by using the right-hand triangle relationship from Equation5. A standard index of refraction was assumed, 1.00029, and a refractiveindex structure coefficient term, Cn², was added for each 5-meter-thickvolume of atmosphere.

To calculate the change in height caused by flowing through many volumesof atmosphere with different indexes of refraction a homogeneous volumeof atmosphere was also calculated, the Control Height. The ControlHeight assumes that there is no change in index of refraction across the100-meter path and uses the same starting angle of 60 degrees. Thedifference between the homogeneous volume of atmosphere and the volumesof air with varying indexes of refraction (IoR) was then calculated asthe Height Delta.

Tables 1A and 1B outline these calculations for the 60-degreepropagation case. The difference in height over 100 meters wascalculated at 0.001525 meters or 0.1525 cm.

TABLE 1A Height Delta from IoR Change Distance Incident Angle IncidentAngle Air (m) (Degrees) (Radians) Height (IoR) 0 60 1.047197551 01.00029 5 59.99996158 1.047196881 8.660241 1.00029 10 59.999957731.047196814 17.32048 1.00029 15 59.99991931 1.047196143 25.98071 1.0002920 59.99991547 1.047196076 34.64093 1.00029 25 59.99987704 1.04719540543.30114 1.00029 30 59.9998732 1.047195338 51.96135 1.00029 3559.99986936 1.047195271 60.62156 1.00029 40 59.99983093 1.047194669.28175 1.00029 45 59.99982709 1.047194533 77.94195 1.00029 5059.99978867 1.047193863 86.60213 1.00029 55 59.99978483 1.04719379695.26231 1.00029 60 59.9997464 1.047193125 103.9225 1.00029 6559.99974256 1.047193058 112.5826 1.00029 70 59.99970414 1.047192387121.2428 1.00029 75 59.99970029 1.04719232 129.9029 1.00029 8059.99966187 1.04719165 138.5631 1.00029 85 59.99965803 1.047191583147.2232 1.00029 90 59.99961961 1.047190912 155.8833 1.00029 9559.99961576 1.047190845 164.5434 1.00029 100 59.99957734 1.047190174173.2036 1.00029

TABLE 1B Height Delta from IoR Change Distance (m) Cn2 IoR ChangeResulting IoR Control Height Height Delta 0 1.50E−13 3.87298E−071.000290387 0 0 5 1.50E−15 3.87298E−08 1.000290039 8.660254038 1.34E−0510 1.50E−13 3.87298E−07 1.000290387 17.32050808 2.82E−05 15 1.50E−153.87298E−08 1.000290039 25.98076211 5.63E−05 20 1.50E−13 3.87298E−071.000290387 34.64101615 8.58E−05 25 1.50E−15 3.87298E−08 1.00029003943.30127019 0.000129 30 1.50E−15 3.87298E−08 1.000290039 51.961524230.000173 35 1.50E−13 3.87298E−07 1.000290387 60.62177826 0.000219 401.50E−15 3.87298E−08 1.000290039 69.2820323 0.000273 45 1.50E−133.87298E−07 1.000290387 77.94228634 0.000338 50 1.50E−15 3.87298E−081.000290039 86.60254038 0.000412 55 1.50E−13 3.87298E−07 1.00029038795.26279442 0.000487 60 1.50E−15 3.87298E−08 1.000290039 103.92304850.000575 65 1.50E−13 3.87298E−07 1.000290387 112.5833025 0.000665 701.50E−15 3.87298E−08 1.000290039 121.2435565 0.000769 75 1.50E−133.87298E−07 1.000290387 129.9038106 0.000873 80 1.50E−15 3.87298E−081.000290039 138.5640646 0.000991 85 1.50E−13 3.87298E−07 1.000290387147.2243186 0.001111 90 1.50E−15 3.87298E−08 1.000290039 155.88457270.001243 95 1.50E−13 3.87298E−07 1.000290387 164.5448267 0.001377 1001.50E−15 3.87298E−08 1.000290039 173.2050808 0.001525

Another way to visualize the effect of Cn² on an optical system is tocalculate the Optical Path Difference (OPD) for a base refractive indexcompared to the base refractive index impacted by Cn². OPD is calculatedfrom knowing a base Optical Path Length (OPL=n₁l) and then a modifiedOPL that uses different refractive indices. OPD is shown in Equation 6.

OPD=|n ₁ l−n ₂ l|  Equation 6

A modified OPD equation can be generated by replacing n₂ in Equation 6with a base index of refraction combined with the square root of therefractive index structure coefficient, Cn².

OPD=|n ₁ l−(n ₁+√{square root over (Cn ²)})l|  Equation 7

where n₁ is the base refractive index, l is the propagation path length,and Cn² is the refractive index structure coefficient. Units of OPD willbe in the same units used for the base length under evaluation.

The implication with an OPD calculation is not that the light will bendbut that the wavefront will become distorted and aberrated as itpropagates through turbulent air. The resulting wavefront will create animage that is blurred. The effect of OPD on the phase of the light canbe calculated by dividing the OPD by a desired wavelength as seen inEquation 8.

Phase Shift=OPD/λ  Equation 8

Equation 8 may be used to make calculations for a wavelength ofinterest, 1064 nm, at various distances and Cn² values. FIG. 6illustrates the maximum phase shift per distance when compared to a baseindex of refraction (1.00029) and an index of refraction value that asthe maximum Cn² disturbance within it (1.00029+√{square root over(Cn²)}). It is noted that for calculations in FIG. 6 and Table 2 aconstant Cn² was used for the calculations.

Table 2 shows the calculations displayed in FIG. 6 resulting from anindex of refraction change because of distance. In the worst case ofatmospheric turbulence that was used for analysis, 1.5 e⁻¹³ m^(−2/3), atthe farthest point, 10,000 m, it is possible to see a phase shift ofover 3,500 waves.

TABLE 2 OPD/λ Calculations for Cn2 E−13 OPD/λ Calculations for Cn2 E−13Distance (m) Air (IoR) Cn2 E−13 IoR Change Resulting IoR OPL OPL Cn2 OPDOPD/λ 0 1.00029 1.50E−13 3.87298E−07 1.000290387 0 0 0 0 500 1.000291.50E−13 3.87298E−07 1.000290387 500.145 500.1452 0.000194 182.0011 10001.00029 1.50E−13 3.87298E−07 1.000290387 1000.29 1000.29 0.000387364.0022 1500 1.00029 1.50E−13 3.87298E−07 1.000290387 1500.435 1500.4360.000581 546.0033 2000 1.00029 1.50E−13 3.87298E−07 1.000290387 2000.582000.581 0.000775 728.0044 2500 1.00029 1.50E−13 3.87298E−07 1.0002903872500.725 2500.726 0.000968 910.0055 3000 1.00029 1.50E−13 3.87298E−071.000290387 3000.87 3000.871 0.001162 1092.007 3500 1.00029 1.50E−133.87298E−07 1.000290387 3501.015 3501.016 0.001356 1274.008 4000 1.000291.50E−13 3.87298E−07 1.000290387 4001.16 4001.162 0.001549 1456.009 45001.00029 1.50E−13 3.87298E−07 1.000290387 4501.305 4501.307 0.0017431638.01 5000 1.00029 1.50E−13 3.87298E−07 1.000290387 5001.45 5001.4520.001936 1820.011 5500 1.00029 1.50E−13 3.87298E−07 1.000290387 5501.5955501.597 0.00213 2002.012 6000 1.00029 1.50E−13 3.87298E−07 1.0002903876001.74 6001.742 0.002324 2184.013 6500 1.00029 1.50E−13 3.87298E−071.000290387 6501.885 6501.888 0.002517 2366.014 7000 1.00029 1.50E−133.87298E−07 1.000290387 7002.03 7002.033 0.002711 2548.015 7500 1.000291.50E−13 3.87298E−07 1.000290387 7502.175 7502.178 0.002905 2730.0168000 1.00029 1.50E−13 3.87298E−07 1.000290387 8002.32 8002.323 0.0030982912.018 8500 1.00029 1.50E−13 3.87298E−07 1.000290387 8502.465 8502.4680.003292 3094.019 9000 1.00029 1.50E−13 3.87298E−07 1.000290387 9002.619002.613 0.003486 3276.02 9500 1.00029 1.50E−13 3.87298E−07 1.0002903879502.755 9502.759 0.003679 3458.021 10000 1.00029 1.50E−13 3.87298E−071.000290387 10002.9 10002.9 0.003873 3640.022

At optical wavelengths, the refractive index of air has a dependence ontemperature and pressure of the environment given by

$\begin{matrix}{n_{1} = {{n - 1} = {\frac{77.6\; P}{T} \times 10^{- 6}}}} & {{Equation}\mspace{14mu} 9}\end{matrix}$

where T is the temperature of the air in degrees Kelvin and P is thepressure of the air in millibars. Temperature will be the dominatingfactor for calculating the index of refraction for air and can be seenwhen taking the derivative of n₁.

$\begin{matrix}{\frac{{dn}_{1}}{dT} = {\frac{{- 77.6}\; P}{T^{2}} \times 10^{- 6}}} & {{Equation}\mspace{14mu} 10}\end{matrix}$

By multiplying both sides of the equation by dT and then changing dT toΔT and dn₁ to Δn₁ the equation changes to:

$\begin{matrix}{{\Delta \; n_{1}} = {\frac{{- 77.6}\; P}{T^{2}} \times 10^{- 6}\Delta \; T}} & {{Equation}\mspace{14mu} 11}\end{matrix}$

Recall that the original n₁({right arrow over (r)},t) is considered arandomly fluctuating term like a signal fluctuating above and belowzero. By squaring n₁({right arrow over (r)},t), and therefore Δn₁, thesignal can be made to a power and evaluated as:

$\begin{matrix}{{\Delta \; n_{1}^{2}} = {\lbrack {\frac{{- 77.6}\; P}{T^{2}} \times 10^{- 6}} \rbrack^{2}\Delta \; T^{2}}} & {{Equation}\mspace{14mu} 12}\end{matrix}$

Which is very similar to published equations that describe Cn² in termsof a temperature structure coefficient Ct²,

C _(n) ²=[79^(P/T) ² ]²×10⁻¹² C _(T) ²  Equation 13

where P is pressure in millibars and T is temperature in degrees Kelvin.The C_(T) ² value can be measured experimentally using differentialtemperature sensors and then calculated using the Kolmogorov spectrum ofturbulence by

$\begin{matrix}{{C_{T}^{2} = \frac{\langle{\Delta \; T^{2}}\rangle}{r^{2/3}}},} & {{Equation}\mspace{14mu} 14}\end{matrix}$

where ΔT is the temperature difference obtained from a pair oftemperature sensors separated by distance r. The angle brackets indicatean ensemble average.

Assuming a differential temperature sensor separation where r=1 m, thenΔT² and C_(T) ² are mathematically identical.

In one embodiment, the desire may be to select instrumentation that isboth low cost, high resolution, and easy to implement. High accuracytemperature sensors, such as thermocouples and anemometers, that havebeen used in previous experiments require high end data collectionequipment that is not low cost or size. Lower cost Resistive TemperatureDetectors (RTD) and thermistors typically do not have the accuracy orresolution required for differential temperature measurements. To betterunderstand requirements for a differential temperature sensor, a set ofcommercial off the shelf (COTS) sensors were evaluated. Minimumresolution from selected sensors were inserted as ΔT into Equation 13and Equation 14 to generate minimum measurable Cn².

Table 3 displays the minimum measurable Cn² variations, based upon theresolution of the COTS temperature sensors. As seen in the table, theminimum resolvable Cn² is a function of minimum sensor resolution.

TABLE 3 COTS Temperature Sensor Trade Study COTS Sensors TSci 506F (10bit) TSci 506F (12 bit) 1083 TMP102 SEN-11931 MPL3115A2 SEN-11084 HRESdT 0.068359375 0.017089844 0.0625 0.029296875 0.00390625 Ct 0.0136639470.000853997 0.011421944 0.002509705  4.4617E−05 Cn 5.91005E−153.69378E−16 4.94032E−15 1.08552E−15 1.92981E−17

To illustrate how critical sensor selection is, in one embodiment, twosensors were evaluated against Cn² data collected on a typical day. Thegoal of the evaluation was to deconstruct a Cn² signal into ΔTincrements and then reconstruct the Cn² data using COTS Sensorresolution. FIG. 8 illustrates Cn² data collected using an AtmosphericCharacterization System (ACS), or wavefront sensor, on May 5, 2015. Thedata from FIG. 8 was converted into C_(T) ² using Equation 15 withvalues of pressure and temperature from Table 4. Data for Table 4 wasextracted from the daily weather provided by the Weather Underground(Weather Underground, 2016) website and is shown in FIG. 7.

$\begin{matrix}{\frac{C_{n}^{2}}{\lbrack \frac{79^{P}}{T^{2}} \rbrack^{2} \times 10^{- 12}} = C_{T}^{2}} & {{Equation}\mspace{14mu} 15}\end{matrix}$

TABLE 4 Values Used for dT Calculations Instrument Measurement UnitsTemperature 295.37 Kelvin Pressure 1023.7 Milibar Sensor Spacing 0.2Meter

Equation 16 was then used to calculate ΔT of the original Cn² signal.

C _(T) ²(r ^(2/3))=

ΔT ²

  Equation 16

Once ΔT increments are populated in Table 3, it is easy to make a sensorselection based upon the minimum Cn² resolution. For comparison, COTSSensors TMP102 SEN-11931 and HRES were selected for reconstruction ofthe original Cn² signal. The signal was reconstructed by taking thecalculated ΔT from Equation 16 and reducing each ΔT at every timeincrement into COTS Sensors resolution steps based upon the sensorminimum resolution using Equation 17.

$\begin{matrix}{\frac{\Delta \; T}{SensorResolution} = {ResolutionSteps}} & {{Equation}\mspace{14mu} 17}\end{matrix}$

The resulting Resolution Steps were rounded to the nearest integernumber and are shown in FIG. 9. Without further analysis it is easy tosee that a higher resolution temperature sensor has many more resolutionsteps to more closely approximate the original Cn² signal.

Rounded temperature sensor Resolution Steps are then multiplied by theirassociated lowest sensor resolution to fully reconstruct the ‘digital’Cn² plot using Equation 18.

ResolutionSteps*SensorResolution=Cn ²  Equation 18

FIG. 10 shows the impact sensor resolution has in correctlyapproximating Cn². The low-resolution sensor TMP102 SEN-11931 followsthe general Cn² trend but the resolution steps are clearly seen whencompared with the original May 5 data. The higher resolution HRES sensordoes a better job of following original May 5 Cn² data with differencesapparent only upon close inspection of FIG. 10 and the enlarged FIG. 11.

FIG. 12 depicts a block diagram of an atmospheric characterizationsystem 1200 in accordance with an embodiment of the present disclosure.The atmospheric characterization system 1200 comprises a centralprocessing board 1203. Further, positioned on opposing sides of theprocessing board 1203 are precision temperature sensors 1201 and 1202.The precision sensors 1201 and 1202 are positioned equidistance from theprocessing board 1203, such that d₁ is equal to d₂. Further, thedistance between the precision temperature sensor 1201 and precisiontemperature sensor 1202 is a predetermined value r.

The precision temperature sensors 1201 and 1202 are shown positionedperpendicularly with respect to the processing board 1203. However, theprecision temperature sensors 1201 and 1202 may be positioned at anangle relative to the processing board 1203, as is shown in FIG. 12. Inthis regard, the precision temperature sensors 1201 and 1202 may bepositioned, for example, at a forty-five-degree angle relative to theprocessing board 1203. Note, however, that the precision temperaturesensors 1201 and 1202 are still positioned an equidistance from theprocessing board 1203, and the precision temperature sensors arepositioned a predetermined distance r one from the other.

Further note that the positioning of the precision temperature sensors1201 and 1202 at a forty-five-degree angle is merely exemplary. Theprecision temperature sensors 1201 and 1202 may be positioned at otherangles relative to the processing board 1203 in other embodiments.

In one embodiment and in accordance with the temperature sensor studydescribed hereinabove, the precision temperature sensors 1201 and 1202may be high resolution HRES 12C digital temperature sensors with aminimum resolution of 0.00390625 degrees Celsius. However, other sensorshaving other resolutions may be used in other embodiments.

A differential temperature is the measurement of a temperaturedifference between precision temperature sensor 1201 and precisiontemperature sensor 1202 that are positioned a distance r one from theother. To allow for sensor spacing, the atmospheric characterizationsystem 1200 incorporates the center processing board 1203 with theseparate precision temperature sensors 1201 and 1202 that arecommunicatively coupled to a data bus on the processing board 1203,which is described further with reference to FIG. 13.

In this regard, the precision temperature sensors 1201 and 1202 arecommunicatively coupled to the processing board via connections 1220 and1221, respectively. In one embodiment, the connections 1220 and 1221 maybe cables for transferring data indicative of measured temperatures tothe processing board 1203 upon demand or periodically.

In another embodiment, the connections 1220 and 1221 may representwireless connections. In such an embodiment, the precision temperaturesensors 1201 and 1202 may each comprise a wireless transceiver. Further,the processing board may comprise a wireless transceiver. Thus, dataindicative of temperature values may be transmitted periodically or upondemand to the processing board 1203 via the wireless connections 1220and 1221.

During operation, each precision temperature sensor 1201 and 1202measures a respective temperature simultaneously. Thereafter, theprecision temperature sensors 1201 and 1202 transmit data indicative ofthe temperatures measured to the processing board 1203 eitherperiodically or upon demand. As will be described further with referenceto FIG. 13, the processing board calculates a value indicative ofatmospheric turbulence, which is described further herein.

The data indicative of atmospheric turbulence may be used to build anatmospheric weather model used to predict, given a certain time of dayand ground temperature, a model for what the atmosphere looks like inelevation versus temperature over time. Notably, the atmosphericturbulence data may be used to correct for temperature changes that benda beam of light in an optical system. As an example, the atmosphericcharacterization system 1200 and a laser system may be co-mounted on aground vehicle. The atmospheric turbulence data received from theatmospheric system 1200 may be used to correct a mirror that deforms thelaser beam so that the laser points straight at a target. In thisregard, the atmospheric turbulence data collected by the atmosphericcharacterization system 1200 may be used to calibrate the laser systemto the surrounding atmospheric conditions.

FIG. 13 depicts an exemplary embodiment of the atmosphericcharacterization system 1200. As shown by FIG. 13, the atmosphericcharacterization system 1200 comprises the precision temperature sensors1201 and 1202 and the processing board 1203.

The processing board 1203 comprises a processor 1204, a temperaturesensor 1206, a pressure sensor 1207, a global positioning system (GPS)1205, and a storage device 1210. Further, the processing board 1203comprises memory 1208 for storing control logic 1209, measured data1215, and calculated data 1216. Note that the measured data 1215 and thecalculated data 1216 may also be stored on an onboard storage device1210, such as a storage device (SD) card.

In one embodiment, the processing board 1203 may comprise a data link1211. In this regard, measured data 1215 and/or calculated data 1216 maybe transferred from the processing board 1203 to another computingdevice (not shown) to use in designing, modifying, or calibrating anoptical system. Additionally, the calculated data 1215 may be used tocorrect an existing onboard optical system.

The control logic 1209 generally controls the functionality of theprocessing board 1203, as will be described in more detail hereafter. Itshould be noted that the control logic 1209 can be implemented insoftware, hardware, firmware or any combination thereof. In an exemplaryembodiment illustrated in FIG. 13, the control logic 1209 is implementedin software and stored in memory 1208.

Note that the control logic 1209, when implemented in software, can bestored and transported on any computer-readable medium for use by or inconnection with an instruction execution apparatus that can fetch andexecute instructions. In the context of this document, a“computer-readable medium” can be any means that can contain or store acomputer program for use by or in connection with an instructionexecution apparatus.

The processor 1204, such as a digital signal processor (DSP) or acentral processing unit (CPU), communicates with and drives the otherelements within the processing board 1203 via at least one bus 1214.Further, the processor 1204 is configured to execute instructions ofsoftware, such as the control logic 1209.

The temperature sensor 1206 is configured to measure an ambienttemperature of the environment in which the atmospheric characterizationsystem is operating. In this regard, the temperature sensor 1206measures the surrounding temperature periodically, and the measuredtemperature is used in generating calculated data 1216, which isdescribed further herein.

The pressure sensor 1207 is configured to measure an ambient pressure ofthe environment in which the atmospheric characterization system isoperating. In this regard, the pressure sensor 1207 measures thesurrounding pressure periodically, and the measured pressure is used ingenerating calculated data 1216, which is described further herein.

To account for accurate time stamps on data collected during operationof the atmospheric characterization system 1200, the GPS 1205 is used toaccurately record location and time. The GPS 1205 allows for manydifferential temperature nodes at separate spatial locations to be usedduring one test with high confidence that recorded time is correct.

The processing board 1203 further comprises precision temperature sensorinterfaces 1212 and 1213. The temperature sensor interfaces 1212 and1214 communicatively couple the processing board 1203 with the precisiontemperature sensors 1201 and 1202, respectively, over connections 1220and 1221, respectively. The precision temperature sensor interfaces 1212and 1213 may be a port for receiving a cable the couples the precisiontemperature sensors 1201 and 1202 to the processing board 1203.

In another embodiment, the connections 1220 and 1221 may be wirelessconnections that communicatively couple the precision temperaturesensors 1201 and 1202 to the precision temperature sensor interfaces1212 and 1214. In such an embodiment, the precision temperature sensors1201 and 1202 comprise a wireless transceiver for sending dataindicative of measured temperature to the processing board 1203.Further, the precision temperature sensor interfaces 1212 and 1213comprise a wireless transceiver for receiving data indicative oftemperature from the precision temperature sensors 1201 and 1202.

In operation, the precision temperature sensors 1201 and 1202periodically measure the atmospheric temperature. Upon request orautomatically, the precision temperature sensors 1201 and 1202 transmitdata indicative of the temperatures measured to the processing board1203.

Upon receipt of the data indicative of the temperatures measured, thecontrol logic 1209 stores the data indicative of the temperaturesmeasured in measured data 1215 correlated with a location and time stamprequested from the GPS 1205.

Upon receipt of the measured data 1215 or periodically, the controllogic calculates a value indicative of atmospheric turbulence at thenoted location and time. In this regard, the control logic 1209calculates a temperature structure coefficient using the followingequation 14 described hereinabove, which is repeated here for clarity:

$\begin{matrix}{{C_{T}^{2} = \frac{\langle{\Delta \; T^{2}}\rangle}{r^{2/3}}},} & {{Equation}\mspace{14mu} 14}\end{matrix}$

wherein the ΔT is the difference between the measured temperature fromprecision temperature sensor 1201 and the measured temperature fromprecision temperature sensor 1202. In this regard, the control logic1209 subtracts the measured temperature from precision temperaturesensor 1201 from the measured temperature from precision temperaturesensor 1202. Further, the r in the dividend is the distance betweenprecision temperature sensor 1201 and precision temperature sensor 1202.The result is the temperature structure coefficient C_(T) ².

The control logic then uses the temperature structure coefficient C_(T)² to obtain a value indicative of the atmospheric turbulence C_(n) ²using equation 13 repeated here for clarity:

C _(n) ²=[79^(P/T) ² ]²×10⁻¹² C _(T) ²,  Equation 13

wherein the P value is the ambient pressure obtained from the pressuresensor 1207, and the T value is ambient temperature obtained from thetemperature sensor 1206.

Once the atmospheric turbulence is calculated, data indicative of theatmospheric turbulence may be stored as calculated data 1216. In thealternative or in addition, the data indicative of the atmosphericturbulence may be stored on the storage device 1210. In one embodiment,the data indicative of the atmospheric turbulence may be transmittedfrom the processing board 1203 to a computing device (not shown) overthe data link 1211.

As described hereinabove, the data indicative of the atmosphericturbulence may then be used to generate an atmospheric weather modelused to predict what the atmosphere looks like in elevation versustemperature over time, which can be used in design of an optics systemto correct for atmospheric effects. Additionally, the data indicative ofatmospheric turbulence may be used to correct an optical system so thata laser of the system points in a straight line to its intended target.Further, the data indicative of atmospheric turbulence may be used tocalibrate an optical system so that the laser accurately points to itsintended target.

Note that during operation, performance of each of the precisiontemperature sensors 1201 and 1202 may be affected by solar radiationwhen exposed to direct sunlight. FIG. 14 depicts an embodiment of theprecision temperature sensors 1201 and 1202 of the atmosphericcharacterization system 1200, wherein each of the precision temperaturesensors 1201 and 1202 are coupled to and protected against directsunlight by respective solar radiation shields 1400 and 1401. The solarradiation shields 1400 and 1401 are configured to allow airflow throughthe sensor housing but not allow any light above the horizon to reachthe precision temperature sensors 1201 and 1202

In this regard, each solar radiation shield 1400 and 1401 comprisesthree conical-shaped layers 1402-1404 and 1405-1407, respectively. Theconical-shaped layers 1402-1404 and 1405-1407 are coupled together;however, a cylindrical opening under each layer allows air to flowthrough the solar radiation shields 1400 and 1401 as indicated byreference arrows 1408 a-1408 f and 1409 a-1409 f. Because the air flowflows through the solar radiation shields 1400 and 1401, the operationof the precision temperature sensors 1201 and 1202 are un affected bythe respective radiation shields 1400 and 1401.

FIG. 15 depicts a cross-sectional view of the solar radiation shield1400. Note that the solar radiation shields 1400 and 1401 are identical.Thus, the description of the solar radiation shield 1400 equally appliesto the solar radiation shield 1401. For simplicity, only one, solarradiation shield 1400, is discussed herein.

The solar radiation shield 1400 comprises the three conical-shapedlayers 1402-1404. The top layer 1402 is coupled to the middle layer 1403via connectors 1500 and 1501. Further, the middle layer 1403 is coupledto the bottom layer via connector 1502. Additionally, the bottom layer1403 is coupled to a bracket 1505.

The precision temperature sensor 1201 comprises a temperature sensor1507 and a printed circuit board 1506 to which the sensor 1507 iselectrically coupled. The printed circuit board 1506 is coupled to thebracket 1505.

Each conical-shaped layer 1402-1404 has a radial opening 1508-1510,respectively. These radial openings 1508-1510 allow air to flow freelythrough the solar radiation shield 1400. Because the air may flow freelythrough the solar radiation shield 1400, operation of the precisiontemperature sensor 1201 is unaffected by direct sunlight and theprecision temperature sensor 1201 is able to still accurately measuresurrounding temperature.

FIG. 16 is a flowchart of the architecture and functionality of theatmospheric characterization system 1200 (FIG. 13).

The processor board 1203 (FIG. 13) periodically or upon demand receivesdata indicative of temperature measurements made by precisiontemperature sensor 1201 and precision temperature sensor 1202 in step1600. The precision temperature sensors 1201 and 1202 are spaced apart adistance r, which is predefined during manufacturing of the atmosphericcharacterization system 1200.

Upon receipt of the data indicative of the temperature measurements, thecontrol logic 1209 obtains a reading from the global positioning system(GPS) 1205. In step 1601, the control logic 1209 associates thetemperature data with a location and time stamp obtained from the GPS1205.

In step 1602, the control logic 1209 calculates a temperature structurecoefficient by using equation 14 described hereinabove. In calculatingthe temperature structure coefficient, the control logic 1209 uses thedifference in temperature between precision temperature sensors 1201 and1202 and the distance r between the precision temperature sensors 1201and 1202.

In step 1603, the control logic 1209 calculates a value indicative ofatmospheric turbulence based upon the temperature structure coefficient,the ambient temperature obtained from temperature sensor 1206 (FIG. 13)and the ambient pressure obtained from pressure sensor 1207 (FIG. 13).

Once the atmospheric turbulence is calculated in step 1603, in step1604, the atmospheric turbulence values over time may be used to modifyan optical system based upon the atmospheric turbulence value.

What I claim is:
 1. An atmospheric characterization system, comprising:a central processing board comprising a first and a second communicationinterface; a first precision temperature sensor communicatively coupledto the central processing board via the first communication interfaceand positioned a distance from a first side of the processing board, theprecision temperature configured for measuring a first temperature andtransfer data indicative of the first temperature to the centralprocessing board; a second precision temperature sensor communicativelycoupled to the central processing board via the second communicationinterface and positioned the distance from a second opposing side of theprocessing board such that the first precision temperature sensor andthe second precision temperature sensor are equidistance from theprocessing board and a distance between the first precision sensor andthe second precision sensor is a predetermined distance, r, the secondprecision temperature sensor configured for measuring a secondtemperature and transferring data indicative of the second temperatureto the central processing board simultaneously with the transferring ofthe first temperature; and a processor configured for receiving thefirst temperature and the second temperature and calculating a valueindicative of atmospheric turbulence based upon the first temperatureand the second temperature, the value indicative of the atmosphericturbulence used for designing, modifying, calibrating, or correcting anoptical system.
 2. The atmospheric characterization system of claim 1,wherein the first precision temperature sensor and the second precisiontemperature sensor each comprise a cable for connecting to thecommunication interfaces, wherein the first precision temperature sensorand the second precision temperature sensor are configured fortransmitting data indicative of the of the atmospheric turbulence to thecentral processing board over the cables.
 3. The atmosphericcharacterization system of claim 1, wherein the first precisiontemperature sensor and the second precision temperatures sensor eachcomprise a wireless transceiver for communicatively connecting to awireless transceiver on the central processing board, wherein the firstprecision temperature sensor and the second precision temperature sensorare configured for transmitting data indicative of the first temperatureand the second temperature to the central processing board wirelessly.4. The atmospheric characterization system of claim 1, wherein the firstprecision temperature sensor is positioned on the first side of thecentral processing board at an angle relative to the central processingboard and the second precision temperature sensor is positioned on theopposing second side at the angle relative to the processing board. 5.The atmospheric characterization system of claim 1, wherein theprocessor is further configured for calculating a temperature structurecoefficient based upon the first temperature, the second temperature,and the predetermined distance, r.
 6. The atmospheric characterizationsystem of claim 5, wherein the central processing board furthercomprises an ambient temperature sensor configured for detecting anambient temperature and an ambient pressure sensor configured fordetecting an ambient pressure.
 7. The atmospheric characterizationsystem of claim 6, wherein the processor is further configured forcalculating the value indicative of the atmospheric turbulence basedupon the calculated temperature structure coefficient, the ambienttemperature, and the ambient pressure.
 8. The atmosphericcharacterization system of claim 1, wherein each of the first precisiontemperature sensor and the second precision temperature sensor iscoupled to and covered by a first radiation shield and a secondradiation shield, respectively.
 9. The atmospheric characterizationsystem of claim 8, wherein the first and the second radiation shieldeach comprises at least one layer.
 10. The atmospheric characterizationsystem of claim 9, wherein each of the at least one layer of the firstand second radiation shields comprises a radial opening on an undersideof the layers to allow air flow through the first and second radiationshields thereby allowing accurate temperature measurements by the firstprecision temperature sensor and the second precision temperaturesensor.
 11. The atmospheric characterization system of claim 1, whereinthe central processing board further comprises a global positioningsystem (GPS).
 12. The atmospheric characterization system of claim 11,further comprising a storage device (SD) card, wherein the dataindicative of the value of the atmospheric turbulence and dataindicative of an associated location and time obtained from the GPS arestored on the SD card.
 13. The atmospheric characterization system ofclaim 11, wherein the central processing board further comprises a datalink.
 14. The atmospheric characterization system of claim 13, whereinthe data indicative of the value of the atmospheric turbulence and dataindicative of an associated location and time are transmitted to acomputing device via the data link.
 15. An atmospheric characterizationmethod, comprising: measuring a first temperature via a precisiontemperature sensor communicatively coupled to a central processing boardand positioned a distance from a first side of the processing board;measuring a second temperature via a second precision temperature sensorcommunicatively coupled to the central processing board and positionedthe distance from a second opposing side of the processing board suchthat the first precision temperature sensor and the second precisiontemperature sensor are equidistance from the central processing board,and the distance between the first precision sensor and the secondprecision temperature sensor is a predetermined distance, r,transferring data indicative of the first temperature and the secondtemperature sensor to the central processing board simultaneously;receiving, by a processor, the first temperature and the secondtemperature; calculating a value indicative of atmospheric turbulencebased upon the first temperature, the second temperature, and thedistance, r; and designing, modifying, calibrating, or correcting anoptical system based upon the value indicative of the atmosphericturbulence.
 16. The atmospheric characterization method of claim 15,wherein the transferring is completed upon demand from the processor.17. The atmospheric characterization method of claim 15, wherein thetransferring is completed periodically.
 18. The atmosphericcharacterization method of claim 15, wherein the first precisiontemperature sensor and the second precision temperature sensor eachcomprise a cable for communicatively connecting to communicationinterfaces on the central processing board, further comprisingtransmitting data indicative of the first temperature and the secondtemperature to the central processing board over the cables.
 19. Theatmospheric characterization method of claim 15, wherein the firstprecision temperature sensor and the second precision temperature sensoreach comprises a wireless transceiver for communicatively connecting tocommunication interfaces on the central processing board, wherein thecommunication interfaces each comprises a wireless transceiver, furthercomprising transmitting data indicative of the first temperature and thesecond temperature to the central processing board wirelessly.
 20. Theatmospheric characterization method of claim 15, further comprisingcalculating, by the processor, a temperature structure coefficient basedupon the first temperature, the second temperature, and thepredetermined distance, r.
 21. The atmospheric characterization methodof claim 20, wherein the central processing board further comprises anambient temperature sensor and an ambient pressure sensor, furthercomprising: detecting an ambient temperature by the ambient temperaturesensor; and detecting an ambient pressure by the ambient pressuresensor.
 22. The atmospheric characterization method of claim 21, furthercomprising calculating, by the processor, the value indicative of theatmospheric turbulence based upon the calculated temperature structurecoefficient, the ambient temperature, and the ambient pressure.
 23. Theatmospheric characterization method of claim 15, wherein the centralprocessing board further comprises a global positioning systemconfigured for obtaining data indicative of a location and a timeassociated with the first and second temperatures.
 24. The atmosphericcharacterization method of claim 23, wherein the central processingboard further comprises a storage device (SD) card, further comprisingstoring data indicative of the value indicative of the atmosphericturbulence and the associated location and time.
 25. The atmosphericcharacterization method of claim 23, wherein the central processingboard further comprises a data link, further comprising transmitting thedata indicative of the value indicative of the atmospheric turbulenceand the associated location and time to a computing device.